Enhanced common downlink control channels

ABSTRACT

A method is provided for communication in a wireless telecommunication system. The method comprises designating, by a network element, a first set of time-frequency resources for transmitting a first set of downlink control channels for a plurality of UEs, wherein the first set of time-frequency resources is known to the plurality of UEs, and wherein the first set of time-frequency resources varies from a first time interval to a second time interval. The method further comprises mapping, by the network element, a first downlink control channel to the first set of time-frequency resources. The method further comprises transmitting, by the network element, the first downlink control channel together with a downlink data channel in a frequency-division multiplexing manner.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 61/612,804, filed Mar. 19, 2012 by Yufei Wu Blankenship,et al., entitled “Enhanced Common Downlink Control Channels” which isincorporated by reference herein as if reproduced in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to wireless telecommunications systemsand more particularly to control channels in wireless telecommunicationssystems.

BACKGROUND

As used herein, the term “user equipment” (alternatively “UE”) might insome cases refer to mobile devices such as mobile telephones, personaldigital assistants, handheld or laptop computers, and similar devicesthat have telecommunications capabilities. Such a UE might include adevice and its associated removable memory module, such as but notlimited to a Universal Integrated Circuit Card (UICC) that includes aSubscriber Identity Module (SIM) application, a Universal SubscriberIdentity Module (USIM) application, or a Removable User Identity Module(R-UIM) application. Alternatively, such a UE might include the deviceitself without such a module. In other cases, the term “UE” might referto devices that have similar capabilities but that are nottransportable, such as desktop computers, set-top boxes, or networkappliances. The term “UE” can also refer to any hardware or softwarecomponent that can terminate a communication session for a user. Also,the terms “user equipment,” “UE,” “user agent,” “UA,” “user device,” and“mobile device” might be used synonymously herein.

As telecommunications technology has evolved, more advanced networkaccess equipment has been introduced that can provide services that werenot possible previously. This network access equipment might includesystems and devices that are improvements of the equivalent equipment ina traditional wireless telecommunications system. Such advanced or nextgeneration equipment may be included in evolving wireless communicationsstandards, such as long-term evolution (LTE). For example, an LTE systemmight include an Evolved Universal Terrestrial Radio Access Network(E-UTRAN) node B (eNB), a wireless access point, or a similar componentrather than a traditional base station. Any such component will bereferred to herein as an eNB, but it should be understood that such acomponent is not necessarily an eNB. Such a component may also bereferred to herein as an access node.

LTE may be said to correspond to Third Generation Partnership Project(3GPP) Release 8 (Rel-8 or R8) and Release 9 (Rel-9 or R9), and possiblyalso to releases beyond Release 9, while LTE Advanced (LTE-A) may besaid to correspond to Release 10 (Rel-10 or R10) and possibly also toRelease 11 (Rel-11 or R11) and other releases beyond Release 10. As usedherein, the terms “legacy”, “legacy UE”, and the like might refer tosignals, UEs, and/or other entities that comply with LTE Release 10and/or earlier releases but do not fully comply with releases later thanRelease 10. The terms “advanced”, “advanced UE”, and the like mightrefer to signals, UEs, and/or other entities that comply with LTERelease 11 and/or later releases. While the discussion herein deals withLTE systems, the concepts are equally applicable to other wirelesssystems as well.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a diagram of a downlink LTE subframe, according to the priorart.

FIG. 2 is a diagram of an LTE downlink resource grid in the case of anormal cyclic prefix, according to the prior art.

FIG. 3 is a diagram of a mapping of a cell-specific reference signal ina resource block in the case of two antenna ports at an eNB, accordingto the prior art.

FIG. 4 is a diagram of a resource element group allocation in a resourceblock in the first slot when two antenna ports are configured at an eNB,according to the prior art.

FIG. 5 is a diagram of E-PDCCH regions, according to an embodiment ofthe disclosure.

FIG. 6 is a table describing common search space and UE-specific searchspace combinations that a UE is expected to monitor, according to anembodiment of the disclosure.

FIG. 7 is a diagram of an E-PCFICH and an E-PDCCH in the same subframe,according to an embodiment of the disclosure.

FIG. 8 is a diagram of an E-PCFICH and an E-PDCCH in differentsubframes, according to an embodiment of the disclosure.

FIG. 9 is a diagram of an E-PCFICH and an E-PDCCH in the same subframe,according to an embodiment of the disclosure.

FIG. 10 is a diagram of an example of predefined E-PCFICH segments in acell, according to an embodiment of the disclosure.

FIG. 11 is a diagram of a cross-interleaving E-PDCCH region when thereis no legacy PDCCH, according to an embodiment of the disclosure.

FIG. 12 is a diagram of a distribution of an E-PCFICH within a subframe,according to an embodiment of the disclosure.

FIG. 13 is a diagram of a distribution of an E-PHICH within a subframe,according to an embodiment of the disclosure.

FIG. 14 is a diagram of REG to RE mapping in OFDM symbols configured foran E-PHICH, according to an embodiment of the disclosure.

FIG. 15 is another diagram of REG to RE mapping in OFDM symbolsconfigured for an E-PHICH, according to an embodiment of the disclosure.

FIG. 16 is a diagram of mapping of a short REG for an E-PHICH, accordingto an embodiment of the disclosure.

FIG. 17 is a diagram of possible options for common and UE-specificsearch space resource allocation, according to an embodiment of thedisclosure.

FIG. 18 is a diagram of a pointer to a PDSCH of an SI-RNTI, according toan embodiment of the disclosure.

FIG. 19 is a diagram of a cross-interleaving E-PDCCH region relative toPSS/SSS/PBCH, according to an embodiment of the disclosure.

FIG. 20 is a diagram of ICIC of an E-PDCCH common search space betweentwo neighbor cells, according to an embodiment of the disclosure.

FIG. 21 is a diagram of an eCCE index for a localized E-PDCCHtransmission, according to an embodiment of the disclosure.

FIG. 22 is a diagram of a starting index of an eCCE in each E-PDCCHregion, according to an embodiment of the disclosure.

FIG. 23 is a simplified block diagram of an exemplary network elementaccording to one embodiment.

FIG. 24 is a block diagram with an example user equipment capable ofbeing used with the systems and methods in the embodiments describedherein.

FIG. 25 illustrates a processor and related components suitable forimplementing the several embodiments of the present disclosure.

DETAILED DESCRIPTION

It should be understood at the outset that although illustrativeimplementations of one or more embodiments of the present disclosure areprovided below, the disclosed systems and/or methods may be implementedusing any number of techniques, whether currently known or in existence.The disclosure should in no way be limited to the illustrativeimplementations, drawings, and techniques illustrated below, includingthe exemplary designs and implementations illustrated and describedherein, but may be modified within the scope of the appended claimsalong with their full scope of equivalents. Embodiments are describedherein in the context of an LTE wireless network or system, but can beadapted for other wireless networks or systems.

In an LTE system, physical downlink control channels (PDCCHs) are usedto carry downlink (DL) or uplink (UL) data scheduling information, orgrants, from an eNB to one or more UEs. The scheduling information mayinclude a resource allocation, a modulation and coding rate (ortransport block size), the identity of the intended UE or UEs, and otherinformation. A PDCCH could be intended for a single UE, multiple UEs orall UEs in a cell, depending on the nature and content of the scheduleddata. A broadcast PDCCH is used to carry scheduling information for aphysical downlink shared channel (PDSCH) that is intended to be receivedby all UEs in a cell, such as a PDSCH carrying system information aboutthe eNB. A multicast PDCCH is intended to be received by a group of UEsin a cell. A unicast PDCCH is used to carry scheduling information for aPDSCH that is intended to be received by only a single UE.

FIG. 1 illustrates a typical DL LTE subframe 110. Control informationsuch as the PHICH (physical HARQ (hybrid automatic repeat request)indicator channel), PCFICH (physical control format indicator channel),and PDCCH are transmitted in a control channel region 120. The PHICH isused to transmit HARQ acknowledgements and negative acknowledgements(ACK/NACK), which may indicate whether the eNB has correctly receiveduplink scheduled data on the physical uplink shared channel (PUSCH).

The control channel region 120 includes the first few OFDM (orthogonalfrequency division multiplexing) symbols in the subframe 110. The exactnumber of OFDM symbols for the control channel region 120 may bedynamically indicated by a control format indicator (CFI) in the PCFICH,which is transmitted in the first symbol. Alternatively, the number ofOFDM symbols may be semi-statically configured when cross carrierscheduling is configured in the case of carrier aggregation in LTERel-10.

The PDSCH, PBCH (physical broadcast channel), PSC/SSC (primarysynchronization channel/secondary synchronization channel), and CSI-RS(channel state information reference signal) are transmitted in a PDSCHregion 130. DL user data is carried by the PDSCH channels scheduled inthe PDSCH region 130. Cell-specific reference signals are transmittedover both the control channel region 120 and the PDSCH region 130, asdescribed in more detail below.

Each subframe 110 can include a number of OFDM symbols in the timedomain and a number of subcarriers in the frequency domain. An OFDMsymbol in time and a subcarrier in frequency together define a resourceelement (RE). A physical resource block (physical RB or PRB) can bedefined as, for example, 12 consecutive subcarriers in the frequencydomain and all the OFDM symbols in a slot in the time domain. An RB orPRB pair with the same RB index in slot 0 (140 a) and slot 1 (140 b) ina subframe can be allocated together.

FIG. 2 shows an LTE DL resource grid 210 within each slot 140 in thecase of a normal cyclic prefix (CP) configuration. The resource grid 210is defined for each antenna port, i.e., each antenna port has its ownseparate resource grid 210. Each element in the resource grid 210 for anantenna port is an RE 220, which is uniquely identified by an index pairof a subcarrier and an OFDM symbol in a slot 140. An RB 230 includes anumber of consecutive subcarriers in the frequency domain and a numberof consecutive OFDM symbols in the time domain, as shown in the figure.An RB 230 is the minimum unit used for the mapping of certain physicalchannels to REs 220.

For DL channel estimation and demodulation purposes, cell-specificreference signals (CRSs) can be transmitted over each antenna port oncertain pre-defined time and frequency REs in every subframe. CRSs areused by Rel-8 to Rel-10 legacy UEs to demodulate the control channels.FIG. 3 shows an example of CRS locations in a subframe for two antennaports 310 a and 310 b, where the RE locations marked with “R0” and “R1”are used for CRS port 0 and CRS port 1 transmission, respectively. REsmarked with “X” indicate that nothing should be transmitted on thoseREs, as CRSs will be transmitted on the other antenna.

Resource element groups (REGs) are used in LTE for defining the mappingof control channels such as the PDCCH to REs. A REG includes either fouror six consecutive REs in an OFDM symbol, depending on whether the CRSsare included. For example, for the two-antenna port CRSs shown in FIG.3, the REG allocation in each RB is shown in FIG. 4, where the controlregion 410 includes two OFDM symbols and different REGs are indicatedwith different types of shading. REs marked with “R0” or “X” in FIG. 4 aor with “R1” or “X” in FIG. 4 b are reserved for CRSs for antenna port 0and antenna port 1, and therefore only four REs in each REG areavailable for carrying control channel data.

A PDCCH can be transmitted on an aggregation of one or more consecutivecontrol channel elements (CCEs), where one CCE consists of, for example,nine REGs. The CCEs available for a UE's PDCCH transmission are numberedfrom 0 to n_(CCE)−1.

The number of CCEs available in a subframe depends on the systembandwidth and the number of OFDM symbols configured for the controlregion. For example, in a 10 MHz system with three OFDM symbolsconfigured for the control region and six groups configured for thePHICH, 42 CCEs are available for the PDCCH.

Multiple PDCCHs may be multiplexed in the control region in a subframeto support UL and DL data scheduling for one UE and to support DL and ULscheduling for more than one UE. For a given system bandwidth, thenumber of PDCCHs that can be supported in the control region alsodepends on the aggregation level used for each PDCCH. The aggregationlevel indicates how many CCEs are aggregated to carry a PDCCH. Theaggregation level for a given target packet error rate is determined bythe downlink received signal quality at a UE and the size of thedownlink control information (DCI) to be carried by a PDCCH. In general,a high aggregation level is needed for a PDCCH intended for a UE that isat the cell edge and is far away from the serving eNB, or when a DCIwith a large payload size is used.

The legacy PDCCH region in LTE may have capacity issues for some newapplications or deployment scenarios where the number of scheduled UEsin a subframe could be large. Some examples include multiple usermultiple input multiple output (MU-MIMO) transmission, coordinatedmulti-point (COMP) transmission, heterogeneous network (hetnet)deployment with remote radio heads (RRHs) in a cell sharing the samecell ID, and carrier aggregation (CA). With these deployment scenarios,there may be a need to enhance the capacity of the PDCCH.

One approach for PDCCH capacity enhancement is to transmit DCI in thelegacy PDSCH region. That is, some PRBs or PRB pairs in the traditionalPDSCH region can be reserved for DCI transmission to UEs. Hereinafter, aphysical downlink control channel transmitted in the legacy PDSCH regionwill be referred to as an extended or enhanced PDCCH (E-PDCCH). A set ofRBs and OFDM symbols or PRB pairs reserved for this purpose can bereferred to as an E-PDCCH region. The E-PDCCH region in a subframe isnot necessarily completely filled with E-PDCCHs in that some resourcesin the E-PDCCH region not used for E-PDCCH transmission can be assignedfor PDSCH transmission. In addition, for some scenarios, the legacyPDCCH region may or may not be present in a subframe containing anE-PDCCH region. The time and frequency resources of an E-PDCCH regionmay be configurable. Examples of E-PDCCH regions are shown in FIG. 5.

With the introduction of the E-PDCCH, the other two downlink controlchannels, the PHICH and the PCFICH, may also exist in extended orenhanced forms, which may be referred to as the E-PHICH and theE-PCFICH, respectively. Several challenges may arise with regard to theE-PHICH and the E-PCFICH. First, E-PDCCH resource allocation in asubframe with an E-PCFICH may need to be dynamically indicated. That is,the presence of the E-PCFICH may need to be signaled to UEs, thelocation of the E-PCFICH may need to be specified and signaled to UEs,the E-PCFICH may need to be multiplexed with the E-PDCCH and the PDSCH,and the information content carried by the E-PCFICH may need to bedetermined. Second, a common search space in the E-PDCCH region may needto be defined. Third, inter-cell interference management for theE-PCFICH, E-PHICH, and E-PDCCH common search space may need to beconsidered. Fourth, the design and reuse of reference signals forE-PCFICH and E-PHICH demodulation may need to be considered. Fifth,ACK/NACK resources in the physical uplink control channel (PUCCH) for acorresponding uplink grant transmitted by the E-PDCCH may need to bedetermined.

Furthermore, in the legacy control region, a common search space (CSS)and a UE-specific search space (USS) that a Rel-8/9/10 UE is expected tomonitor to detect the PDCCH have been defined. With the introduction ofenhanced control channels in the data region, another set of CSS and USSmay be defined for the E-PDCCH. In Table 1 in FIG. 6, the CSS and USScombinations that a UE is expected to monitor are shown. The table showsthat there are multiple scenarios that may need a common search spacefor the E-PDCCH in the data region.

While these combinations show what an individual UE is expected tomonitor, all other UEs do not necessarily monitor the same combinationsfor a given subframe. Thus, the embodiments disclosed herein mayconsider the prevailing scenario where a CSS is defined in the dataregion. This may correspond to any scenario in Table 1 where a CSS of adata region is marked ‘Yes’. Whenever a legacy control region ismentioned, it may be assumed that the carrier is a normal carrier withCFI greater than 0.

Since the CSS is shared by multiple UEs, the CSS may need to reside in apredefined common resource area. Over the common resource area, otherdownlink channels such as the E-PCFICH and the E-PHICH may bemultiplexed in. Thus, the embodiments disclosed herein may cover a rangeof issues related to such a common resource area, including how theE-PCFICH and the E-PHICH may be multiplexed with the E-PDCCH, how theREs are allocated to the control channels, and other topics.

Embodiments of the present disclosure may also provideE-PDCCH/E-PHICH/E-PCFICH designs for subframes that may not contain thelegacy PDCCH region. The embodiments may also enable UEs that are notcapable of monitoring the legacy PHICH and PDCCH to receive controlinformation from an eNB. Some embodiments may have a context in whichthe component carrier where the PDSCH is transmitted does not usecross-carrier scheduling. The PDSCH may be scheduled by the controlchannel of the same component carrier. To avoid decoding two PCFICHinstances, for cross-carrier scheduled transmissions, the start of thedata region may not be obtained from the PCFICH on that componentcarrier, but may be configured on a semi-static basis via radio resourcecontrol (RRC) signaling. Also, in some contexts, when a common searchspace is discussed, it may be assumed that the component carrier is theprimary component carrier for the UE under consideration. The commonsearch space may only be defined for transmissions on the primarycomponent carrier.

An application example where the embodiments described herein may applyis the case of a new carrier type in a carrier aggregation scenariowhere, to reduce overhead, there is no legacy PDCCH region defined onthe new carrier. Another application example where the embodiments mayapply is in the support of machine type communication (MTC), wherein aUE may not be required to receive signals over the entire bandwidth andthus may not receive the entire legacy control region. Anotherapplication example where the embodiments may apply is the case of avictim cell in a heterogeneous network scenario. For example, if stronginterference from an aggressor cell makes it difficult to receive thesignal in part of the legacy control region, then the UE may receivedownlink control information via E-PDCCH/E-PHICH/E-PCFICH instead.

More specifically, at least six sets of embodiments are provided hereinto deal with enhanced common downlink control channels. A first set ofembodiments deals with E-PCFICH resource allocation and signaling, asecond set of embodiments deals with E-PHICH resource allocation andconfiguration, a third set of embodiments deals with a common searchspace in the E-PDCCH, a fourth set of embodiments deals withcoordination of E-PDCCH allocation with fixed signals, a fifth set ofembodiments deals with coordination in E-PDCCH allocation betweenneighbor cells or transmission points, and a sixth set of embodimentsdeals with PUCCH resource mapping.

In the first set of embodiments, resource allocation and signaling of anE-PCFICH are provided so that an advanced UE can detect the E-PCFICH(when configured) from a predefined region without excessive delay. Inan embodiment, a master information block (MIB) may be used for E-PCFICHindication in a cell. This may inform an advanced UE whether or not anE-PCFICH is present in a cell. In an embodiment, if an E-PCFICH ispresent, a cell ID and/or subframe-dependent E-PCFICH resourceallocation within a subframe may be predefined without any signaling. Inan embodiment, an E-PDCCH resource in a subframe may be signaled throughan E-PCFICH in either the same subframe or a previous subframe. In anembodiment, the detection of a common search space in an E-PDCCH may beactivated via RRC signaling.

The E-PCFICH can carry parameters that define the shared E-PDCCH controlregion so that the scheduling of the E-PDCCH can be changed dynamically.It may be expected that such a shared E-PDCCH control region would usecross-interleaving, where E-PDCCHs from multiple UEs are interleaved andmultiplexed together. In the following discussion, such a region isreferred to as a cross-interleaving region.

When cross-interleaving is used for multiplexing of multiple E-PDCCHs,the PRB pairs allocated for the E-PDCCH cannot be used by the PDSCH.This can lead to resource waste if the resources provisioned for PRBsexceed the actual E-PDCCHs to be carried for a given subframe. Forexample, if the subframe needs to support one UE, then at most twoE-PDCCHs are needed for UE-specific signaling, one for downlinkscheduling assignments, one for uplink scheduling grants. If thesubframe needs to support 10 UEs, then up to 20 E-PDCCHs are needed forUE-specific signaling. Thus, the number of PRB pairs needed to support10 UEs is much greater than the number of PRB pairs needed to supportone UE. Therefore, a balance between E-PDCCH capacity and overhead mayneed to be made. In this case, the E-PCFICH may be useful to dynamicallyindicate the E-PDCCH allocation in each subframe based on the actualnumber of UEs to be scheduled. This may reduce overhead and increaseoverall efficiency of resource utilization.

If the E-PCFICH is used for dynamic indication of the E-PDCCHcross-interleaving region in a subframe, then the E-PCFICH may need tobe detected first, independently of other information. The E-PCFICH mayneed to be transmitted over known resources, with a known transmitformat, and its resource location within a subframe may in principle beindependent of the E-PDCCH allocation. In other words, it may bedesirable to have a preconfigured allocation for the E-PCFICH in eachsubframe, where the preconfigured allocation is known to all UEsconfigured to monitor the E-PCFICH. However, allocating one or more PRBsor PRB pairs exclusively for the E-PCFICH may introduce too muchoverhead. To reduce E-PCFICH overhead and also to increase frequencydiversity, the E-PCFICH may be multiplexed with the E-PDCCH. That is,the E-PCFICH may share some of the PRBs or PRB pairs configured for theE-PDCCH. For example, a region for interleaved E-PDCCHs can bepredefined, and the E-PCFICH can be allocated to the first one or thefirst few OFDM symbols of the interleaved region. Additionally, theE-PCFICH can be distributed over a wide frequency range to obtainfrequency diversity.

The E-PCFICH may need to rely on a certain type of common referencesignal for channel estimation, where the reference signal can be used bymultiple UEs. Such a common reference signal may be a local commonreference signal. For example, the common reference signal may bedefined for the interleaved region only, which is in contrast to the CRSwhich is common to an entire cell covering the entire spectrum. Theselocal common reference signals may be received as demodulation referencesignals (DMRS) for the E-PCFICH by the UEs.

Time-wise, it may be desirable to have the E-PCFICH (if defined) locatedtowards the beginning of the subframe, as shown in FIG. 7, so that theE-PCFICH can be decoded as early as possible. This may reduce theprocessing delay of the E-PDCCH and PDSCH decoding at the UE.

Alternatively, an E-PDCCH region in a subframe may be indicated by anE-PCFICH in a previous subframe as shown in FIG. 8. With this option,the E-PDCCH region in a subframe may be determined at the start of thesubframe and the E-PCFICH transmitted in the previous subframe may beallocated across the whole subframe without delay concern. In yetanother option, which is a variant of the scheme shown in FIG. 8, theE-PCFICH in a subframe may be used for the configuration of the E-PDCCHregions starting in the next subframe. Such an E-PDCCH configuration maybe assumed for the subsequent subframes until a new E-PCFICH isdetected. Further, the periodicity and offset of an E-PCFICHtransmission may be semi-statically defined, e.g., in units of subframeor radio frame. The UE may attempt detection of the E-PCFICH only incertain known time instances and skip E-PCFICH detection otherwise.

While these options provide benefits such as reduced E-PCFICH overheadand having the E-PCFICH available before a subframe is received, theseoptions may have some impact on a UE in idle or DRX mode, where a legacyUE may need to be able to detect a possible DCI within a subframeperiod. So to support cross-subframe resource indication, the wakeuptime for an advanced UE in idle or DRX mode may need to be increased totwo or more subframe durations in order for the UE to detect a DCI.Alternatively, a DCI may always be transmitted in the legacy PDCCHregion for advanced UEs in idle or DRX mode. Thus, the parameters ofthese options may need to be selected carefully to balance the benefitsand drawbacks.

Frequency-wise, the E-PCFICH may need to be located in predefined PRBs,possibly a subset of PRBs that are occupied by the E-PDCCH region withcross-interleaving. This is illustrated in FIG. 9, where it is assumedthat the E-PCFICH resides within two known PRB segments, each with nRBs, in the cross-interleaving E-PDCCH region. Moreover, the two knownPRB segments are not contiguous in frequency so that frequency diversitycan be obtained. Here, integer n is smaller than or equal to half thenumber of total PRBs occupied by the cross-interleaving E-PDCCH region.For completeness, FIG. 9 illustrates the legacy PDCCH (assuming itexists) and the E-PHICH as well.

As an example, to provide the known PRB segments, it can be defined thatthe upper frequency segment starts at a PRB with index:└N _(PRB) ^(tot)/2┘+Δ_(offset) +N _(PRB) ^(segment)×((Y _(k) mod(N_(PRB) ^(common)/(2·N _(PRB) ^(segment))))),  (1)and that the lower frequency segment starts at a PRB with index:└N _(PRB) ^(tot)/2┘−Δ_(offset) −N _(PRB) ^(segment)×((Y _(k) mod(N_(PRB) ^(common)/(2·N _(PRB) ^(segment))))+1),  (2)

Here it is assumed that the PRBs are numbered from 0 to N_(PRB)^(tot)−1. Variable N_(PRB) ^(segment) is the number of PRBs in asegment, and there are two segments of equal size. N_(PRB) ^(tot) is thetotal number of PRBs for the cell, N_(PRB) ^(common) is the number ofPRBs that can be used for the cross-interleaving region of the E-PDCCH,N_(PRB) ^(common)≦N_(PRB) ^(tot) and N_(PRB) ^(common) is a multiple of(2·N_(PRB) ^(segment)). Variable Δ_(offset), where Δ_(offset)≧0 andΔ_(offset)≦└N_(PRB) ^(tot)/2┘−N_(PRB) ^(common)/2, is the segment offsetin units of PRBs, which measures the distance between the first segmentand the center of the bandwidth. In particular, when Δ_(offset)>0, thehigher and lower frequency segments are guaranteed to be separated by atleast 2×Δ_(offset) in frequency. The variables needed to define thesegments, N_(PRB) ^(common), N_(PRB) ^(segment), Δ_(offset) may bepredefined or provided via RRC signaling through the legacy PDCCH. Thevariable Y_(k) is defined byY _(k)=(A·Y _(k-1))mod D  (3)where Y⁻¹=N_(ID) ^(cell) is the cell ID ranging from 0 to 503, A=39827,D=65537 and k=└n_(s)/2┘. n_(s) is the slot number within a radio frame.The concept is shown in FIG. 10.

While the example describes using two segments equally spaced withrespect to the center of the bandwidth, other schemes are possible topredefine resources known to both the eNB and the UE. For example, thescheme can be two segments defined with respect to the edges of thebandwidth. In another example, the scheme can be N_(seg) segments evenlyspaced starting from the lower PRB index, where N_(seg) is an integer.In yet another example, the scheme can be N_(seg) segments evenly spacedstarting from the higher PRB index.

If an advanced carrier has no legacy PDCCH region, then thecross-interleaving E-PDCCH region can span the entire subframe time-wiseas shown in FIG. 11.

The presence of an enhanced control channel such as the E-PCFICH mayneed to be signaled to a UE. If the legacy PDCCH is present and the UEis able to receive control information over the legacy PDCCH, the UE mayreceive the control signal in the legacy PDCCH region first. Thepresence of the E-PCFICH and its resource allocation may then besemi-statically signaled. For some UEs, such as a UE with MTC, theE-PCFICH may need to be signaled before any RRC signaling, since MTC UEsmay not have the capability to detect the signal in the whole legacycontrol region. One possibility is for the presence of the E-PCFICH tobe indicated in the MIB, which is carried over the PBCH.

At least two options exist for multiplexing the E-PCFICH with the PDSCH.In frequency division multiplexing (FDM) or PRB pair-based multiplexing,the E-PCFICH may be allocated within one or multiple PRB pairs. Incombined FDM and time division multiplexing (TDM) or PRB-basedmultiplexing, the E-PCFICH may be allocated within one or multiple PRBsin the first slot. Only the PDSCH for advanced UEs can be multiplexedwith the E-PCFICH in this case. When E-PCFICH is transmitted in the PRBsthat are also used for E-PDCCH transmission, then the multiplexing ofthe E-PCFICH with the PDSCH follows how the E-PDCCH is multiplexed withthe PDSCH.

At least three options exist for signaling the E-PCFICH resourceallocation to UEs. In a first option, E-PCFICH resources are predefinedin common locations for all cells. In this case, no signaling is needed,but there could be inter-cell interference issues. In a second option,E-PCFICH resources are predefined as a function of cell ID and perhapssubframe number. This option is illustrated in the example of FIG. 10.In a third option, E-PCFICH resources are RRC signaled. This optionassumes that the legacy PDCCH is present and that all UEs are capable ofreceiving downlink and uplink grants in the legacy PDCCH region.

For CoMP scenario 4, if only parameters common to the transmissionpoints (TPs) are used in defining the E-PCFICH resource (e.g., cell ID,subframe number), the same E-PCFICH resource location may be used forall TPs in a cell. To further separate out E-PCFICHs for the TPs of thesame cell, additional parameters and resource dimensions may be used,such as using code division multiplexing (CDM) to multiplex theE-PCFICHs of the TPs. Alternatively, TP-specific parameters such asthose related to CSI-RS configuration for the TP could be used to createshifts for the E-PCFICH resources for each TP.

To ensure higher estimation reliability, it may be desirable to allocatethe E-PCFICH to REs that are adjacent to the REs for a reference signal,as shown in FIG. 12.

The information carried in the E-PCFICH may be different from that inthe PCFICH. In the legacy PCFICH, two bits are used to generate fourstates (with one state being reserved), which indicates the number ofOFDM symbols for the control region. In the case of the E-PCFICH, tospecify the RB locations of the E-PDCCH, a full-scale resourceallocation may be needed for more flexibility. The number of bits neededdepends on both bandwidth and resource allocation type. For a 20 MHzbandwidth, 25 bits are needed for resource allocation type 0/1, and 13bits are needed for resource allocation type 2. This is quite largecompared to the PCFICH, and substantial resources may be consumed inorder to reach all UEs in a cell. It is effectively equivalent tosending a DCI. To achieve the same bit error rate (BER) as the PCFICH,four to eight CCEs may be needed, similar to DCI 1A/1C transmission inthe common search space of the legacy PDCCH, which is equivalent to twoto three distributed RB pairs. Such resource consumption may beexcessive compared to the PCFICH.

Thus, simpler information may need to be defined for the E-PCFICH. Forexample, the E-PCFICH may take four values (e.g., 1, 2, 3, 4), eachindicating a different number of PRBs relative to an anchor PRBposition. The anchor PRB may be either predefined or RRC signaled. To bemore specific, these four values may represent four states, eachindicating a subset of the E-PDCCH resources configured by RRC signalingand indicating the number of PRBs and their locations. In one example,values of {1, 2, 3, 4} may represent, respectively, that ¼, ½, ¾, or 1portion of the E-PDCCH resources configured by RRC are used in thecurrent subframe for the actual E-PDCCH. The locations of these PRBs maybe predefined, and the principle used to select such PRBs may be thatthey are evenly spread in the frequency domain to gain frequencydiversity. For example, if RRC configures 10 PRBs as E-PDCCH resources,the E-PCFICH taking the value “1” indicates that round(10/4)=2 PRBs areused in the current subframe for the E-PDCCH, and their logical indexwould be the first and sixth PRBs. In another example, the E-PCFICHtaking the value “2” could mean that round(10×2/4)=5 PRBs are used inthe current subframe for the E-PDCCH, and their logical index would befirst, third, fifth, seventh, and ninth. Similar meanings for E-PCFICHvalues of “3” and “4” can be formulated. With such definitions, only twobits are needed, and the E-PCFICH indicates those PRBs actually used inthe current subframe for the E-PDCCH, while the remaining PRBsconfigured by RRC may be released for PDSCH transmission.

In another example, values of {1, 2, 3, 4} could represent that {N1, N2,N3, N4} PRB pairs are used for the E-PDCCH, where the actual PRBsindicated by {N1, N2, N3, N4} are a function of the bandwidth. The PRBpairs may be evenly spaced across the bandwidth, and their positions maybe a function of the physical cell ID and/or the subframe index.

While in the above it is assumed that the E-PCFICH is transmitted, theE-PCFICH does not necessarily need to be transmitted. In the absence ofthe E-PCFICH, a UE may need to detect the cross-interleaving E-PDCCHregion via other means. For UEs or carriers with a legacy PDCCH, thepresence of the E-PDCCH region as well as the resource allocation of theregion may be RRC signaled, either with UE-specific RRC signaling or asa broadcast to all UEs as part of the system information blocks (SIBs).For UEs that may not be able to decode a legacy PDCCH or for carriersthat do not have a legacy PDCCH, the presence of an E-PDCCH region mayneed to be signaled in the MIB. If an E-PDCCH region is present, apredefined common search space within the E-PDCCH region may be used fortransmitting all the downlink and uplink grants until a UE is configuredwith the rest of the E-PDCCH region for a UE-specific search space.

In general, this set of embodiments provides for transmitting a firstdownlink control channel over a first set of resource elements that arefrequency-division multiplexed with downlink data channels andinterleaved with a second set of resource elements. The second set ofresource elements carries a second downlink control channel. The firstdownlink control channel carries configuration information for a seconddownlink control channel. The first set of resource elements may beknown to a plurality of UEs.

More specifically, in an embodiment, an E-PCFICH channel is introducedin LTE to dynamically indicate the resource allocation of an E-PDCCHwith a distributed transmission. The presence of an E-PCFICH may beindicated by an existing reserved bit in the MIB carried by the PBCH.The resources for the E-PCFICH may be predefined and known to a UE andmay share a subset of PRB pairs configured for the E-PDCCH. The PRBpairs that contain the E-PCFICH may be FDM multiplexed with the PDSCH,and the locations of such PRB pairs may vary from cell to cell. Theresources for the E-PCFICH may be allocated in the first slot of asubframe and may be close to the reference signals. The content of theE-PCFICH may consist of a bit string representing one of a number ofpredefined resource configurations. The E-PDCCH resource configurationindicated by the E-PCFICH may be for an E-PDCCH transmitted in the samesubframe or for an E-PDCCH transmitted in a different subframe, such asa subsequent subframe.

A second set of embodiments disclosed herein deals with E-PHICH resourceallocation and configuration for achieving good channel estimationperformance. In an embodiment, the E-PHICH is mapped to REs close toDMRS REs. REG-to-RE mapping is provided to achieve transmit diversity ofthe E-PHICH.

With the introduction of the E-PDCCH, there may be a need to provide ahigh capacity to carry a large number of ACK/NACKs. Therefore, there maybe a need to enhance the PHICH channel that carries ACK/NACKs. Such anenhanced PHICH channel can be referred to as an E-PHICH channel.Enhancement of the PHICH may be especially necessary considering uplinkMU-MIMO and applications such as MTC. Unlike the relay backhaul link,the downlink ACK/NACK signal cannot be replaced by an uplink new orretransmission grant exclusively without a dedicated ACK/NACK channel,such as the PHICH, since a UE may not have relatively constant downlinkdata. The resource allocation requirements for the E-PHICH may need tobe carefully selected in order for robust performance of the E-PHICH tobe maintained. In an embodiment, the E-PHICH is distributed to OFDMsymbols containing or near the local common DMRS or to OFDM symbolsadjacent thereto. REs adjacent to the REs used for reference signaltransmission may be allocated to carry downlink control informationwhere high reliability is desired, such as the E-PHICH, since REs closeto reference signals tend to have more reliable channel estimationinformation. As illustrated in FIG. 13, this may ensure good channelestimation performance for the E-PHICH.

In FIG. 13, it is assumed that a CSI-RS is not transmitted in thesubframe. All REs in OFDM symbols {4, 5, 6, 7, 11, 12, 13} (highlightedwith horizontal lines) that are not used as reference symbols are usedfor the E-PHICH. Thus, there are a total of 48 REs in a PRB pairavailable for the E-PHICH. If the E-PHICH uses the same bit-to-symbolprocessing as the PHICH, then each E-PHICH group occupies 12 REs,assuming a normal cyclic prefix. Thus, each PRB can transmit fourE-PHICH groups. The same number of E-PHICH groups may be defined as forthe PHICH. That is,N _(PHICH) ^(group) =┌N _(g)(N _(RB) ^(DL)/8)┐, for normal cyclicprefix  (4)where N_(PHICH) ^(group) is the number of PHICH groups and N_(g) is avariable provided by higher layers. Then the number of PRBs the E-PHICHoccupies is N_(PHICH) ^(group)/4. Thus, the fraction of PRBs out oftotal PRBs that the E-PHICH will occupy is

$\begin{matrix}{{\frac{N_{PHICH}^{group}/4}{N_{RB}^{DL}} \approx {N_{g}/32}},{{for}\mspace{14mu}{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}} & (5)\end{matrix}$

For an extended cyclic prefix, approximately the same fraction of PRBsis needed to carry the E-PHICH. Moreover, since the maximum value ofN_(g) is 2, the maximum fraction of PRBs occupied by the E-PHICH is1/16. This would provide sufficient latitude for interferencecoordination between neighbor cells.

When the network is time division duplexed (TDD), and uplink-downlinkconfiguration 0 is used, subframes #0 and #5 need twice as many E-PHICHgroups as otherwise. Thus, the fraction of PRBs occupied by the E-PHICHis ⅛, which is still sufficient to avoid interference between twoneighbor cells.

When a CSI-RS is transmitted in a subframe, the number of useful REs inan OFDM symbol {5, 6, 12, 13} will be reduced. In the worst case ofeight CSI-RS ports, the number of REs usable to transmit the E-PHICH isreduced to 40 from 48. Still, each PRB can transmit three E-PHICH groupsfor a normal cyclic prefix. The fraction of PRBs that need to beassigned to carry the E-PHICH is approximately N_(g)/24, which is notexcessive.

As the E-PHICH carries ACK/NACK information for multiple UEs, thedemodulation of the E-PHICH may have to rely on reference signals sharedby multiple UEs, such as un-precoded DMRS. This may make it difficult tomultiplex the E-PHICH with other types of transmissions that useUE-specific reference signals, such as a PDSCH with beamforming or aUE-specific E-PDCCH. On the other hand, the E-PHICH can be easilymultiplexed with an E-PDCCH that uses a shared reference signal that isof a cross-interleaved type and can carry common information. Even whena common search space does not exist in a subframe, there can still beUE-specific E-PDCCHs that are cross-interleaved and use a sharedreference signal.

Similar to Rel-8 to Rel-10, an REG may be defined in each OFDM symbolallocated for the E-PHICH. In OFDM symbols that do not contain DMRSand/or CSI-RS, the same REG definition as in Rel-8 may be used. That is,an REG is composed of four consecutively available REs in one OFDMsymbol in an RB configured for a potential E-PHICH, where an RE isassumed to be unavailable with respect to the mapping of the E-PHICH ifit is used for transmission of CRS. If CRS is configured for port 0, itmay be assumed that REs for transmission of CRS port 1 are alsounavailable for the REG. Precoded transmit diversity (TxD) symbols for2-tx and 4-tx as defined in Rel-8 may be mapped within each REG.

In OFDM symbols containing DMRS and/or CSI-RS, the options describedbelow may be used for REG definition. The REGs used for a particulardownlink channel (e.g., E-PHICH) may then be selected using a predefinedrule, such as a rule defined in Rel-8.

An REG is composed of four consecutively available REs in one OFDMsymbol in an RB configured for potential E-PHICH transmission counted inascending order of subcarriers. An RE is assumed to be unavailable withrespect to mapping the E-PHICH if the RE is configured for transmissionof a DMRS or if the RE is configured for a CSI-RS.

For an REG={RE(k₁), RE(k₂), RE(k₃), RE(k₄)}, where k_(i) (i=1, 2, 3, 4)are the subcarrier indices of the REs, the following conditions may besatisfied,k ₂ −k ₁ =k ₃=1  (6)

That is, RE(k₁) and RE(k₂) are adjacent REs, as are RE(k₃) and RE(k₄).This condition may ensure that the propagation channels areapproximately the same for each of the RE pairs, which is desirable fortransmit diversity. One such example is shown in FIG. 14. This kind ofmapping may be appropriate for the space frequency block code (SFBC)type of transmit diversity. While a CSI-RS is not included in FIG. 14,the same principle may apply for a subframe containing a CSI-RS.

To further maintain orthogonality between E-PHICHs within an E-PHICHgroup, the propagation channels over an REG should be approximately thesame. For this purpose, further restrictions may be applied to an REG,such as k₄−k₁<5.

Alternatively, for REGs in OFDM symbols containing a DMRS and/or aCSI-RS and configured for potential E-PHICH transmission, an REG iscomposed of four neighboring available REs in an RB in two consecutiveOFDM symbols containing a DMRS and/or a CSI-RS counted in ascendingorder of OFDM symbols first and then subcarriers. An RE is assumed to beunavailable with respect to mapping the E-PHICH if the RE is used forthe transmission of a reference signal such as a DMRS or a CSI-RS.

One such example is shown in FIG. 15, where the following conditions areimposed for an REG={RE1, RE2, RE3, RE4}: RE1 and RE2 are adjacent REs,either in the frequency domain or the time domain; RE3 and RE4 areadjacent REs, either in the frequency domain or the time domain; and themaximum separation of the REs within an REG in the frequency domain isfive REs.

With this type of mapping, the space time block code (STBC) type oftransmit diversity may be needed in the OFDM symbols containing a DMRSand/or a CSI-RS, so a hybrid transmit diversity with SFBC and STBC maybe needed.

With the above resource mapping, E-PHICHs may be multiplexed, scrambled,modulated, mapped to layers, and precoded in the same way as for thelegacy PHICH except that transmit diversity uses DMRS ports fordemodulation instead of CRS ports. The DMRSs in those RBs are shared bymultiple UEs and thus should not be precoded.

In the above discussion, the legacy DMRS is used as an example forE-PDCCH and E-PHICH demodulation. Alternatively, new demodulationreference signals may be defined for the E-PDCCH and the E-PHICH. Ingeneral, the reference symbols for cross-interleaving the E-PDCCH regionmay need to be known to multiple UEs. That is, the reference symbols maynot be specific to a single UE. Unlike a conventional CRS, these sharedreference signals are only local common reference signals and do notneed to be transmitted across the entire bandwidth.

For CoMP scenario 4, the shared reference signals may be TP-specific, sothat all UEs attached to a same TP can access the E-PDCCH common searchspace specific to the given TP. Channel-independent precoding may beassumed by the UE for these shared reference signals.

Defining REGs of four REs for the PHICH may make it easy to support 4-txTxD. This may also lead to the use of an orthogonal covering code (OCC)with a length of 4 to separate ACK/NACK signals in a CDM fashion in eachPHICH group. In Rel-8, the PDCCH, the PHICH, and the PCFICH use the sameREG as the basic unit and are all transmitted in the legacy PDCCHregion, so it may be easy to map these kinds of REGs to the physicaltime-frequency resource grid.

In Rel-11 and beyond, the E-PHICH may be transmitted in the PDSCHregion. Therefore, it may not be easy to map an REG of four REs to thephysical time-frequency resource grid because the REs that are alreadyused for other purposes, such as a DMRS or a CSI-RS, may need to beskipped. As seen from FIG. 14, some REs in an REG may be separated toofar from each other after mapping, which may cause performancedegradation due to the loss of orthogonality among OCC in the case of ahighly frequency selective channel. To solve this issue, instead ofusing four REs per REG as discussed above, a modified E-PHICH group witha smaller size of REGs may be defined, where the new REG consists of twoREs instead of four. Length-2 OCC may then be applied to each E-PHICH inan E-PHICH group in each of the three REGs. Either 2-tx or 4-tx transmitdiversity with SFBC+FSTD may still be used.

The modified E-PHICH group consists of three REGs each with two REs, soeach E-PHICH group could multiplex four ACK/NACK bits. The size of eachE-PHICH group is reduced by half as compared with a Rel-8 PHICH group,so for the same given RE resources, the number of E-PHICH groups isdoubled. This could maintain the overall E-PHICH capacity unchanged. Thedecoding of the E-PHICH may use the DMRS ports, and using two DMRS portsto support 2-tx TxD would cut the DMRS overhead by half as compared withusing four DMRS ports to support 4-tx TxD. The performance gain of 4-txTxD over 2-tx TxD as observed for a Rel-8 PDCCH is less than 1 dB, andthis gain could be offset by the overhead reduction and other benefitsof using 2-tx TxD. A smaller size REG for an E-PHICH group may avoid theloss of orthogonality of OCCs in certain REGs with four REs due to largeseparations of REs.

FIG. 16 shows some examples of mapping such smaller size of REGs to thetime-frequency grid, where “1” and “2” indicate the first and second REsin an REG. Compared with FIG. 14, there are no occasions where the REsin an REG are separated by two to three reserved REs.

For this modified E-PHICH, the derivation of the E-PHICH group index andOCC index in the E-PHICH group for an ACK/NACK from the particular UEmay use the formulas from Rel-8, with a corresponding E-PHICH groupnumber and N_(SF) ^(PHICH)=2, which is the spreading factor of the OCCwithin each E-PHICH group.

In general, this set of embodiments provides for multiplexing the HARQresponse signals of a plurality of UEs over the same time-frequencyresources. The same time-frequency resources are frequency-divisionmultiplexed with a data transmission. Configuration informationregarding the time-frequency resources is signaled to the plurality ofUEs before a HARQ response signal is transmitted.

More specifically, in an embodiment, the resources used for E-PHICHtransmission may be allocated close to the DMRS ports for more accuratechannel estimation. The REGs for the E-PHICH may be defined byconsecutive REs on the same OFDM symbols or by neighboring REs on twoconsecutive OFDM symbols. The number of REs in each REG may be two orfour. 2-tx or 4-tx transmit diversity schemes may be used to transmitthe E-PHICH. While here an REG of size 2 or 4 has been used as anexample of a resource allocation unit, other resource units can be usedas well. For example, a size of m by n rectangle in the time-frequencygrid can be used as a resource allocation unit, where m and n areintegers greater than or equal to 1. Furthermore, while transmitdiversity has been used as an example of a MIMO scheme, other schemessuch as beamforming, spatial multiplexing, MU-MIMO can be used instead.

A third set of embodiments disclosed herein deals with a common searchspace over the E-PDCCH. In an embodiment, a common search space issupported in an E-PDCCH region with cross-interleaving operation. DCIswith the cyclic redundancy check (CRC) scrambled by a system informationradio network temporary identifier (SI-RNTI) are transmitted in both thelegacy PDCCH and the E-PDCCH. DCIs with the CRC scrambled by a paging orrandom access channel RNTI (P-/RA-RNTI) are sent over the legacy PDCCHfor legacy UEs and over a common search space in the E-PDCCH region foradvanced UEs.

For subframes that have a legacy control region, the common search spaceof the E-PDCCH may start immediately after the legacy control region.The number of OFDM symbols in the legacy control region is indicated bya control channel indicator (CFI) carried by the PCFICH. So the commonsearch space may start from OFDM symbol # k, where k=CFI for a systembandwidth greater than 10 PRBs and k=CFI+1 for other system bandwidths(assuming the OFDM symbol index in a subframe starts at 0).Alternatively, the common search space may always start at apreconfigured OFDM symbol, such as OFDM symbol #3 (assuming the OFDMsymbol index in a subframe starts at 0).

Both a common search space and a UE-specific search space may need to bedefined over the E-PDCCH. There are at least three options in definingthe resources for the common search space vs the UE-specific searchspace, as illustrated in FIG. 17.

In the first option, as shown in FIG. 17 a, the resources for the commonsearch space in the E-PDCCH may not overlap with the resources for theUE-specific search space. In other words, separate resources (e.g.,PRBs) may be allocated for the common and UE-specific search spaces. Inthis case, two E-PDCCH regions are defined and a UE searches each regionfor common and UE-specific DCIs. A benefit of this option is thatUE-specific DCI detection could be simpler, since only one E-PDCCHregion may need to be monitored for that purpose. A drawback is that ifthe resource allocation for the common search space is predefined orsemi-statically allocated, some of the resources may be wasted if thereis no common DCI to send.

In the second option, as shown in FIG. 17 b, the resources for thecommon search space in the E-PDCCH may overlap with the resources forthe UE-specific search space. That is, a single E-PDCCH region may bedefined for both search space types. In this case, better resourceutilization may be achieved for the common search space. However, ifDCIs are cross-interleaved and the PRBs are predefined orsemi-statically signaled, overhead could increase if few DCIs need to besent.

In the third option, as shown in FIG. 17 c, two E-PDCCH regions may bepresent in a subframe. One E-PDCCH region may be for a localizedtransmission that is exclusively for the UE-specific search space.Another E-PDCCH region may be a distributed region shared by both thecommon search space and the UE-specific search space. A UE may beconfigured to search in both the regions for UE-specific DCIs and commonDCIs. In this case, better resource utilization may be expected comparedwith the first and second options, even with semi-static resourceallocation for the common search space, but possibly at the cost ofincreased UE implementation complexity.

In all three options, the resource for the common search space in theE-PDCCH region is predefined and known. In the case of the first option,there are two E-PDCCH regions in a subframe, one with distributedtransmission where DCIs may be cross-interleaved and the other withlocalized transmission where DCIs are not cross-interleaved. Thedistributed transmission region may be exclusively for the common searchspace, where multiple DCIs may be cross-interleaved. The PRBs for thedistributed transmission region may be either predefined or signaledthrough the E-PCFICH. The UE-specific search space may be exclusively inthe localized transmission region. Depending on the multiplexing methodfor DCI, different DCIs in the UE-specific search space may bemultiplexed in either the PRB/PRB pair level or the sub-PRB/PRB pairlevel. In the case of the second option, only one E-PDCCH region withdistributed transmission is present in a subframe. The region may bepredefined or signaled through the E-PCFICH. All DCIs may becross-interleaved. In this case, the common search space may occupy aknown subset of the total resources, and the resources for the commonsearch space may also be overlapped with the UE-specific search space.In the case of the third option, the distributed region may also beshared by the common search space and the UE-specific search space. Theresource for the common search space may be predefined.

If both the legacy PDCCH region and the E-PDCCH common search space arepresent, there could be confusion about where the UEs should search forthe common information whose CRC is scrambled by a SI-RNTI, P-RNTI, orRA-RNTI. Since an SI-RNTI is common between legacy UEs and advanced UEs,the common information may need to be transmitted over the legacy PDCCHregion. This information may be repeated in the E-PDCCH common searchspace if an advanced UE (e.g., MTC) cannot or will not detect the legacyPDCCH region. Only one PDSCH carrying a given system information payloadis transmitted in a subframe (i.e., not repeated). Only the pointer tothe PDSCH is repeated. This is shown in FIG. 18.

For a P-RNTI or an RA-RNTI, considering that there may be asubstantially larger number of UEs that need to be signaled (e.g., MTC),the paging and random access-related messages may be divided into atleast three scenarios. In a first scenario, some UEs may be defined toreceive the common information in the legacy PDCCH region only. This setof UEs may include all legacy UEs (Rel-10 or earlier). In a secondscenario, some UEs may be defined to receive the common information inthe E-PDCCH common search space only. This set of UEs may include allMTC types of UEs. For MTC, the differentiation may be performed in arelatively straightforward manner by the scheduler. In a third scenario,some UEs may be configured to receive the common information in eitherthe common search space in the legacy PDCCH or the common search spacein the E-PDCCH. For example, if the common search space in the E-PDCCHis not configured, the UE may search the common search space in thelegacy PDCCH region. Otherwise, the UE may search the common searchspace in the E-PDCCH region. Such UEs may include UEs in Rel-11 andbeyond.

It may be noted that no UE is required to monitor both the common searchspace in the legacy PDCCH region and the common search space in theE-PDCCH region in a given subframe. Therefore, the number of blinddecodings that a specific UE is expected to perform for decoding such aPDCCH may not increase.

A UE capable of detecting DCIs in a common search space in both thelegacy PDCCH and the E-PDCCH may need to understand whether or not tosearch a common search space in an E-PDCCH region. In one embodiment, acommon search space is always present within the E-PDCCH region, so nosignaling is required to indicate the need to detect the common searchspace over the E-PDCCH. This may be unavoidable if the network needs toserve MTC UEs that may not have access to the entire legacy controlregion. For other UEs and with the legacy PDCCH, detecting or notdetecting the common search space in the E-PDCCH may be configured byRRC signaling. That is, a UE may be RRC signaled through the legacyPDCCH about whether to perform a search in a common search space in theE-PDCCH region.

With DCIs carried over a common search space, a UE may obtain all thesystem information in the downlink and, after successful access, may beinformed about the UE-specific E-PDCCH configuration through RRCsignaling. Before being informed about the UE-specific E-PDCCHconfiguration, a UE may have to depend on the legacy PDCCH for receivingall downlink and uplink grants.

For a UE that is not capable of detecting DCIs in the legacy PDCCHregion, both common and UE-specific search spaces may need to be presentin a subframe. PRBs or PRB pairs for the common search space may beeither dynamically indicated through the E-PCFICH or predefined. Theresources for the common search space within the PRBs/PRB pairs may bepredefined. PRBs/PRB pairs for a UE-specific search space may be thesame as the PRBs/PRB pairs for the common search space or may bedifferent. When different PRBs/PRB pairs are used, the PRBs/PRB pairsmay need to be predefined.

Single antenna transmission or transmit diversity may be configured fora common search space. The antenna number for a common search spacetransmission may be derived from broadcast information such as the PBCHor may be RRC configured if the antenna number is different from thatused for the legacy PDCCH. Therefore, no explicit signaling may beneeded to inform the UE which transmission mode is used for a commonsearch in the E-PDCCH. Alternatively, the common search space could betransmitted over a number of distributed resources, e.g., one, two orfour PRBs, across the frequency. In addition to distributed resourceallocation for the common search space, either a transmit diversityscheme or random beamforming may be applied in the common search spacetransmission to further exploit diversity gain.

In general, this set of embodiments provides for transmitting a downlinkcontrol channel by frequency-division multiplexing with downlink datachannels. A time-frequency resource that can be occupied by the downlinkcontrol channel is known to a plurality of UEs and varies from a firsttime interval to a second time interval. The downlink control channelmay carry information associated with the SI-RNTI, the P-RNTI, theRA-RNTI, or the C-RNTI.

More specifically, in an embodiment, a common search space may bedefined and configured in the E-PDCCH. The common search space in theE-PDCCH may or may not overlap with the UE-specific search space. Thecommon search space may overlap with the distributed UE-specific searchspace. The common search space may be used to carry system messages andUE-specific messages. A UE may be configured to monitor one commonsearch space in either the legacy PDCCH or the E-PDCCH. The commonsearch space may be present in all E-PDCCHs or the common search spacemay be configured by higher-layer signaling such as RRC signaling. Thecommon search space may be transmitted over a number of distributedresources. A transmit diversity scheme may be used, with the antennanumber being derived either from the PBCH or from RRC signaling.

A fourth set of embodiments disclosed herein deals with coordination ofE-PDCCH allocation with fixed signals, such as the primarysynchronization signal (PSS), secondary synchronization signal (SSS),and PBCH. In an embodiment, frequency division multiplexing between across-interleaving E-PDCCH region and the fixed signals in a subframe(e.g., PSS/SSS/PBCH) is provided so that these predefined signals andchannels can coexist without any overlap.

If present, the cross-interleaving E-PDCCH search region may need tocoexist with the PSS/SSS/PBCH in a same subframe. In an embodiment, fora bandwidth greater than 1.4 MHz, PRBs for a common search space areallocated immediately above and immediately below the PSS/SSS/PBCH, asshown in FIG. 19. Broadly speaking, the PRBs for the cross-interleavingE-PDCCH region may be any PRBs that do not contain existing signals andchannels such as PSS/SSS or PBCH.

In general, this set of embodiments provides for transmitting a commonsignal over a set of predefined frequency resources and transmitting ashared downlink control channel over a second set of frequencyresources. The second set of frequency resources may be non-overlappingwith the predefined frequency resources when the shared downlink controlchannel is transmitted simultaneously with the common signal. The commonsignal may be a synchronization signal or a physical broadcast channel.The shared downlink control channel may be an E-PCFICH, an E-PHICH, oran E-PDCCH.

A fifth set of embodiments disclosed herein deals with coordination inE-PDCCH allocation between neighbor cells or transmission points.Inter-cell interference coordination (ICIC) may be a motivator indefining the enhanced downlink control channels. In an embodiment,different cells allocate the E-PCFICH and the E-PHICH in non-overlappingresource blocks as much as possible to achieve interference avoidanceand/or interference randomization. Additionally or alternatively,different cells map the E-PCFICH and the E-PHICH to non-overlappingresource elements as much as possible to achieve interference avoidanceand/or interference randomization. The resources allocated to theE-PCFICH, the E-PHICH, and the cross-interleaving E-PDCCH region may becommunicated to neighbor cells for interference avoidance purposes.

One advantage of the E-PDCCH over the legacy PDCCH is the possibilityfor better coordination of interference between adjacent cells. Tooptimize performance, it may be desirable to avoid allocating the samePRBs to the cross-interleaving E-PDCCH of adjacent cells.

In an embodiment, three sets of non-overlapping resources are defined,each corresponding to the cell ID carried by the primary synchronizationsignal of the cell. This is illustrated with an example in FIG. 20. Inpractical deployments, it may not be possible to always achieveinterference avoidance or to achieve interference avoidance with asimple algorithm. In an embodiment, interference randomization is usedin conjunction with interference avoidance. For example, thecross-interleaving region may be a pseudo-random function of thephysical cell ID and the subframe index. Even if two neighbor cellshappen to overlap in one subframe, they are unlikely to overlap in thenext subframe.

Alternatively, if the overlapping E-PDCCH resources are allocated amongneighbor cells or TPs, the resource units may be shifted based on thecell ID (or TP ID or CSI-RS resource associated with the TP). Such ashift may protect the E-PCFICH and, more importantly, the E-PHICH, andmay avoid the collision of such channels from neighbor cells or TPs. Forexample, indices of the REGs that the E-PCFICH and the E-PHICH occupymay be generated with a function of cell ID. Alternatively, theresources allocated to the E-PCFICH, the E-PHICH, and thecross-interleaving E-PDCCH region may be communicated to neighbor cellsvia the X2 interface for interference coordination purposes.

In general, this set of embodiments provides for transmitting a firstshared downlink control channel from a first time-frequency resource bya first transmission point and transmitting a second shared downlinkcontrol channel from a second time-frequency resource by a secondtransmission point. The first shared downlink control channel and thesecond downlink control channel may carry the same downlink controlinformation. Non-overlapping of the first time-frequency resource withthe second time-frequency resource may be achieved by coordinating thetransmissions of the first and the second transmission points. The samedownlink control information may be a HARQ-ACK response or configurationinformation of another downlink control channel. The coordinating may beperformed by a base station or other access node that is connected toboth the first transmission point and the second transmission point. Thecoordinating may be performed by exchanging information between thefirst transmission point and the second transmission point.

More specifically, in an embodiment, resources for the E-PDDCH, E-PCFICHand E-PHICH from different cells may be shifted based on the cell ID orother TP-related parameters (e.g., TP ID) to avoid collisions andmitigate interference.

A sixth set of embodiments disclosed herein deals with PUCCH resourcemapping. In LTE Rel-8, the resource used to transmit a HARQ ACK/NACKover the PUCCH is linked to the index of the first CCE of thecorresponding PDCCH carrying the downlink grant. If the E-PDCCH isintroduced, this implicit relationship may need to be re-evaluated.

In an embodiment, implicit indication of PUCCH resources via E-PDCCHresources is provided. The index of the first resource unit of theE-PDCCH may be used to indicate the PUCCH resource. If multiple E-PDCCHregions are configured, the index of the starting resource unit of eachregion may be signaled to a UE to ensure that the UE can generate adistinct PUCCH resource for each corresponding E-PDCCH.

Two types of E-PDCCH transmission may be supported. One is localizedtransmission, where the E-PDCCH for a UE occupies contiguous resourceswithin an E-PDCCH region. The other is distributed transmission, wherean E-PDCCH occupies non-contiguous resources and E-PDCCHs for multipleUEs are multiplexed and transmitted from the same set of PRBs or PRBpairs. In the latter case, if the CCE structure as defined in Rel-8 isre-used, the mapping between the CCE index and the PUCCH resource couldbe reused. In localized transmission, as the CCE structure may not bethe same as in Rel-8, the implicit mapping relation between the CCEindex and the PUCCH resource may need to be redefined.

In localized E-PDCCH transmission, a new resource unit may be used,which consists of a subset of the resource elements in a PRB pair. Sucha unit can be referred to as an eCCE (enhanced CCE). If multipleE-PDCCHs are transmitted using localized transmission, as shown in FIG.21, their eCCEs may be arranged in a queue and assigned with indices inascending order. In this case, the UE may still use the first eCCE indexof an E-PDCCH to generate a resource for its corresponding PUCCHtransmission.

For the case where there are multiple E-PDCCH regions configured, anoffset for a region may be signaled to a UE, which may be configured tosearch this region for its E-PDCCH. This is illustrated in FIG. 22. TheUE may use the sum of the offset and the index of the first eCCE of anE-PDCCH to derive the corresponding PUCCH resource index. Alternatively,the UE may use the sum of the offset and the index of the last eCCE ofan E-PDCCH to derive the corresponding PUCCH resource index. The offsetof each E-PDCCH region may be selected such that all the correspondingPUCCH resource indices for the region are not overlapped with the PUCCHresource indices for other E-PDCCH regions and the legacy PDCCH region.The offsets may be sent semi-statically to the UE using higher layersignaling as part of the UE E-PDCCH configuration.

In general, the PUCCH resource for transmitting ACK/NACK signals may beimplicitly linked to an eCCE index of the corresponding E-PDCCH.

The embodiments disclosed herein provide a detailed design of theE-PCFICH, the E-PHICH, and the common search space of the E-PDCCH.Signaling procedures for the enhanced control channels are described, asis resource allocation within a subframe, taking into consideration theDMRS distribution. Inter-cell interference management of the commoncontrol channels is also taken into account. PUCCH resource mappingprocedures for the E-PDCCH are provided and embodiments are disclosedthat allow PUCCH resource generation in an implicit way.

The above may be implemented by a network element. A simplified networkelement is shown with regard to FIG. 23. In FIG. 23, network element3110 includes a processor 3120 and a communications subsystem 3130,where the processor 3120 and communications subsystem 3130 cooperate toperform the methods described above.

Further, the above may be implemented by a UE. An example of a UE isdescribed below with regard to FIG. 24. UE 3200 may comprise a two-waywireless communication device having voice and data communicationcapabilities. In some embodiments, voice communication capabilities areoptional. The UE 3200 generally has the capability to communicate withother computer systems on the Internet. Depending on the exactfunctionality provided, the UE 3200 may be referred to as a datamessaging device, a two-way pager, a wireless e-mail device, a cellulartelephone with data messaging capabilities, a wireless Internetappliance, a wireless device, a smart phone, a mobile device, or a datacommunication device, as examples.

Where the UE 3200 is enabled for two-way communication, it mayincorporate a communication subsystem 3211, including a receiver 3212and a transmitter 3214, as well as associated components such as one ormore antenna elements 3216 and 3218, local oscillators (LOs) 3213, and aprocessing module such as a digital signal processor (DSP) 3220. Theparticular design of the communication subsystem 3211 may be dependentupon the communication network in which the UE 3200 is intended tooperate.

Network access requirements may also vary depending upon the type ofnetwork 3219. In some networks, network access is associated with asubscriber or user of the UE 3200. The UE 3200 may require a removableuser identity module (RUIM) or a subscriber identity module (SIM) cardin order to operate on a network. The SIM/RUIM interface 3244 istypically similar to a card slot into which a SIM/RUIM card may beinserted. The SIM/RUIM card may have memory and may hold many keyconfigurations 3251 and other information 3253, such as identificationand subscriber-related information.

When required network registration or activation procedures have beencompleted, the UE 3200 may send and receive communication signals overthe network 3219. As illustrated, the network 3219 may consist ofmultiple base stations communicating with the UE 3200.

Signals received by antenna 3216 through communication network 3219 areinput to receiver 3212, which may perform such common receiver functionsas signal amplification, frequency down conversion, filtering, channelselection, and the like. Analog to digital (A/D) conversion of areceived signal allows more complex communication functions, such asdemodulation and decoding to be performed in the DSP 3220. In a similarmanner, signals to be transmitted are processed, including modulationand encoding for example, by DSP 3220 and are input to transmitter 3214for digital to analog (D/A) conversion, frequency up conversion,filtering, amplification, and transmission over the communicationnetwork 3219 via antenna 3218. DSP 3220 not only processes communicationsignals but also provides for receiver and transmitter control. Forexample, the gains applied to communication signals in receiver 3212 andtransmitter 3214 may be adaptively controlled through automatic gaincontrol algorithms implemented in DSP 3220.

The UE 3200 generally includes a processor 3238 which controls theoverall operation of the device. Communication functions, including dataand voice communications, are performed through communication subsystem3211. Processor 3238 also interacts with further device subsystems suchas the display 3222, flash memory 3224, random access memory (RAM) 3226,auxiliary input/output (I/O) subsystems 3228, serial port 3230, one ormore keyboards or keypads 3232, speaker 3234, microphone 3236, othercommunication subsystem 3240 such as a short-range communicationssubsystem, and any other device subsystems generally designated as 3242.Serial port 3230 may include a USB port or other port currently known ordeveloped in the future.

Some of the illustrated subsystems perform communication-relatedfunctions, whereas other subsystems may provide “resident” or on-devicefunctions. Notably, some subsystems, such as keyboard 3232 and display3222, for example, may be used for both communication-related functions,such as entering a text message for transmission over a communicationnetwork, and device-resident functions, such as a calculator or tasklist.

Operating system software used by the processor 3238 may be stored in apersistent store such as flash memory 3224, which may instead be aread-only memory (ROM) or similar storage element (not shown). Theoperating system, specific device applications, or parts thereof, may betemporarily loaded into a volatile memory such as RAM 3226. Receivedcommunication signals may also be stored in RAM 3226.

As shown, flash memory 3224 may be segregated into different areas forboth computer programs 3258 and program data storage 3250, 3252, 3254and 3256. These different storage types indicate that each program mayallocate a portion of flash memory 3224 for their own data storagerequirements. Processor 3238, in addition to its operating systemfunctions, may enable execution of software applications on the UE 3200.A predetermined set of applications that control basic operations,including at least data and voice communication applications forexample, may typically be installed on the UE 3200 during manufacturing.Other applications may be installed subsequently or dynamically.

Applications and software may be stored on any computer-readable storagemedium. The computer-readable storage medium may be tangible or in atransitory/non-transitory medium such as optical (e.g., CD, DVD, etc.),magnetic (e.g., tape), or other memory currently known or developed inthe future.

One software application may be a personal information manager (PIM)application having the ability to organize and manage data itemsrelating to the user of the UE 3200 such as, but not limited to, e-mail,calendar events, voice mails, appointments, and task items. One or morememory stores may be available on the UE 3200 to facilitate storage ofPIM data items. Such a PIM application may have the ability to send andreceive data items via the wireless network 3219. Further applicationsmay also be loaded onto the UE 3200 through the network 3219, anauxiliary I/O subsystem 3228, serial port 3230, short-rangecommunications subsystem 3240, or any other suitable subsystem 3242, andinstalled by a user in the RAM 3226 or a non-volatile store (not shown)for execution by the processor 3238. Such flexibility in applicationinstallation may increase the functionality of the UE 3200 and mayprovide enhanced on-device functions, communication-related functions,or both. For example, secure communication applications may enableelectronic commerce functions and other such financial transactions tobe performed using the UE 3200.

In a data communication mode, a received signal such as a text messageor web page download may be processed by the communication subsystem3211 and input to the processor 3238, which may further process thereceived signal for output to the display 3222, or alternatively to anauxiliary I/O device 3228.

A user of the UE 3200 may also compose data items, such as emailmessages for example, using the keyboard 3232, which may be a completealphanumeric keyboard or telephone-type keypad, among others, inconjunction with the display 3222 and possibly an auxiliary I/O device3228. Such composed items may then be transmitted over a communicationnetwork through the communication subsystem 3211.

For voice communications, overall operation of the UE 3200 is similar,except that received signals may typically be output to a speaker 3234and signals for transmission may be generated by a microphone 3236.Alternative voice or audio I/O subsystems, such as a voice messagerecording subsystem, may also be implemented on the UE 3200. Althoughvoice or audio signal output may be accomplished primarily through thespeaker 3234, display 3222 may also be used to provide an indication ofthe identity of a calling party, the duration of a voice call, or othervoice call-related information, for example.

Serial port 3230 may be implemented in a personal digital assistant(PDA)-type device for which synchronization with a user's desktopcomputer (not shown) may be desirable, but such a port is an optionaldevice component. Such a port 3230 may enable a user to set preferencesthrough an external device or software application and may extend thecapabilities of the UE 3200 by providing for information or softwaredownloads to the UE 3200 other than through a wireless communicationnetwork. The alternate download path may, for example, be used to loadan encryption key onto the UE 3200 through a direct and thus reliableand trusted connection to thereby enable secure device communication.Serial port 3230 may further be used to connect the device to a computerto act as a modem.

Other communications subsystems 3240, such as a short-rangecommunications subsystem, are further optional components which mayprovide for communication between the UE 3200 and different systems ordevices, which need not necessarily be similar devices. For example, thesubsystem 3240 may include an infrared device and associated circuitsand components or a Bluetooth™ communication module to provide forcommunication with similarly enabled systems and devices. Subsystem 3240may further include non-cellular communications such as WiFi, WiMAX,near field communication (NFC), and/or radio frequency identification(RFID). The other communications element 3240 may also be used tocommunicate with auxiliary devices such as tablet displays, keyboards orprojectors.

The UE and other components described above might include a processingcomponent that is capable of executing instructions related to theactions described above. FIG. 25 illustrates an example of a system 3300that includes a processing component 3310 suitable for implementing oneor more embodiments disclosed herein. In addition to the processor 3310(which may be referred to as a central processor unit or CPU), thesystem 3300 might include network connectivity devices 3320, randomaccess memory (RAM) 3330, read only memory (ROM) 3340, secondary storage3350, and input/output (I/O) devices 3360. These components mightcommunicate with one another via a bus 3370. In some cases, some ofthese components may not be present or may be combined in variouscombinations with one another or with other components not shown. Thesecomponents might be located in a single physical entity or in more thanone physical entity. Any actions described herein as being taken by theprocessor 3310 might be taken by the processor 3310 alone or by theprocessor 3310 in conjunction with one or more components shown or notshown in the drawing, such as a digital signal processor (DSP) 3380.Although the DSP 3380 is shown as a separate component, the DSP 3380might be incorporated into the processor 3310.

The processor 3310 executes instructions, codes, computer programs, orscripts that it might access from the network connectivity devices 3320,RAM 3330, ROM 3340, or secondary storage 3350 (which might includevarious disk-based systems such as hard disk, floppy disk, or opticaldisk). While only one CPU 3310 is shown, multiple processors may bepresent. Thus, while instructions may be discussed as being executed bya processor, the instructions may be executed simultaneously, serially,or otherwise by one or multiple processors. The processor 3310 may beimplemented as one or more CPU chips.

The network connectivity devices 3320 may take the form of modems, modembanks, Ethernet devices, universal serial bus (USB) interface devices,serial interfaces, token ring devices, fiber distributed data interface(FDDI) devices, wireless local area network (WLAN) devices, radiotransceiver devices such as code division multiple access (CDMA)devices, global system for mobile communications (GSM) radio transceiverdevices, universal mobile telecommunications system (UMTS) radiotransceiver devices, long term evolution (LTE) radio transceiverdevices, worldwide interoperability for microwave access (WiMAX)devices, and/or other well-known devices for connecting to networks.These network connectivity devices 3320 may enable the processor 3310 tocommunicate with the Internet or one or more telecommunications networksor other networks from which the processor 3310 might receiveinformation or to which the processor 3310 might output information. Thenetwork connectivity devices 3320 might also include one or moretransceiver components 3325 capable of transmitting and/or receivingdata wirelessly.

The RAM 3330 might be used to store volatile data and perhaps to storeinstructions that are executed by the processor 3310. The ROM 3340 is anon-volatile memory device that typically has a smaller memory capacitythan the memory capacity of the secondary storage 3350. ROM 3340 mightbe used to store instructions and perhaps data that are read duringexecution of the instructions. Access to both RAM 3330 and ROM 3340 istypically faster than to secondary storage 3350. The secondary storage3350 is typically comprised of one or more disk drives or tape drivesand might be used for non-volatile storage of data or as an over-flowdata storage device if RAM 3330 is not large enough to hold all workingdata. Secondary storage 3350 may be used to store programs that areloaded into RAM 3330 when such programs are selected for execution.

The I/O devices 3360 may include liquid crystal displays (LCDs), touchscreen displays, keyboards, keypads, switches, dials, mice, track balls,voice recognizers, card readers, paper tape readers, printers, videomonitors, or other well-known input/output devices. Also, thetransceiver 3325 might be considered to be a component of the I/Odevices 3360 instead of or in addition to being a component of thenetwork connectivity devices 3320.

The following are incorporated herein by reference for all purposes:3GPP TS 36.211, 3GPP TS 36.212, 3GPP TS 36.213, and 3GPP TS 36.331.

In an embodiment, a method for communication in a wirelesstelecommunication system is provided. The method comprises transmitting,by a network element, a downlink control channel over a set of resourceelements, wherein the downlink control channel carries at least oneparameter that configures a control channel region, and wherein thecontrol channel region is frequency-division multiplexed with a downlinkdata channel.

In another embodiment, a network element is provided. The networkelement comprises a processor configured such that the network elementtransmits a downlink control channel over a set of resource elements,wherein the downlink control channel carries at least one parameter thatconfigures a control channel region, and wherein the control channelregion is frequency-division multiplexed with a downlink data channel.

In another embodiment, a method for communication in a wirelesstelecommunication system is provided. The method comprises mapping, by anetwork element, signals of a HARQ-ACK response to a plurality ofresource elements, wherein resource blocks containing signals of theHARQ-ACK response are frequency-division multiplexed with resourceblocks of a data channel, and wherein a configuration of the pluralityof resource elements for the HARQ signals is signaled to UEs beforesignals of the HARQ-ACK response are transmitted. The method furthercomprises transmitting the signals of the HARQ-ACK response.

In another embodiment, a network element is provided. The networkelement comprises a processor configured such that the network elementmaps signals of a HARQ-ACK response to a plurality of resource elements,wherein resource blocks containing signals of the HARQ-ACK response arefrequency-division multiplexed with resource blocks of a data channel,and wherein a configuration of the plurality of resource elements forthe HARQ signals is signaled to UEs before signals of the HARQ-ACKresponse are transmitted. The processor is further configured such thatthe network element transmits the signals of the HARQ-ACK response.

In another embodiment, a method for communication in a wirelesstelecommunication system is provided. The method comprises designating,by a network element, a first set of time-frequency resources fortransmitting a first set of downlink control channels for a plurality ofUEs, wherein the first set of time-frequency resources is known to theplurality of UEs, and wherein the first set of time-frequency resourcesvaries from a first time interval to a second time interval. The methodfurther comprises mapping, by the network element, a first downlinkcontrol channel to the first set of time-frequency resources. The methodfurther comprises transmitting, by the network element, the firstdownlink control channel together with a downlink data channel in afrequency-division multiplexing manner.

In another embodiment, a network element is provided. The networkelement comprises a processor configured such that the network elementdesignates a first set of time-frequency resources for transmitting afirst set of downlink control channels for a plurality of UEs, whereinthe first set of time-frequency resources is known to the plurality ofUEs, and wherein the first set of time-frequency resources varies from afirst time interval to a second time interval. The processor is furtherconfigured such that the network element maps a first downlink controlchannel to the first set of time-frequency resources. The processor isfurther configured such that the network element transmits the firstdownlink control channel together with a downlink data channel in afrequency-division multiplexing manner.

In another embodiment, a method for communication in a wirelesstelecommunication system is provided. The method comprises mapping, by afirst network element, a common signal to a first set of time-frequencyresources in a subframe, wherein the first set of time-frequencyresources is predefined. The method further comprises mapping, by thefirst network element, an enhanced downlink control channel to a secondset of time-frequency resources in the subframe, wherein the first setof time-frequency resources and the second set of time-frequencyresources do not overlap. The method further comprises transmitting, bythe first network element, the common signal and the enhanced downlinkcontrol channel in the same subframe.

In another embodiment, a network element is provided. The networkelement comprises a processor configured such that the network elementmaps a common signal to a first set of time-frequency resources in asubframe, wherein the first set of time-frequency resources ispredefined. The processor is further configured such that the networkelement maps an enhanced downlink control channel to a second set oftime-frequency resources in the subframe, wherein the first set oftime-frequency resources and the second set of time-frequency resourcesdo not overlap. The processor is further configured such that thenetwork element transmits the common signal and the enhanced downlinkcontrol channel in the same subframe.

In another embodiment, a method for communication in a wirelesstelecommunication system is provided. The method comprises mapping, by anetwork element, an E-PDCCH that carries downlink scheduling informationto a UE to indicate a downlink data transmission over a PDSCH to the UE,into a plurality of eCCEs, wherein an eCCE consists of a number ofpredefined REs in an RB pair. The method further comprises linking, bythe network element, a resource index of a PUCCH to an index of one ofthe plurality of eCCEs, wherein the PUCCH is provided for transmitting,by the UE, back to the network element, an ACK or a NACK about adecoding status of the PDSCH.

In another embodiment, a network element is provided. The networkelement comprises a processor configured such that the network elementmaps an E-PDCCH that carries downlink scheduling information to a UE toindicate a downlink data transmission over a PDSCH to the UE, into aplurality of eCCEs, wherein an eCCE consists of a number of predefinedREs in an RB pair. The processor is further configured such that thenetwork element links a resource index of a PUCCH to an index of one ofthe plurality of eCCEs, wherein the PUCCH is provided for transmitting,by the UE, back to the network element, an ACK or a NACK about adecoding status of the PDSCH.

The embodiments described herein are examples of structures, systems ormethods having elements corresponding to elements of the techniques ofthis application. This written description may enable those skilled inthe art to make and use embodiments having alternative elements thatlikewise correspond to the elements of the techniques of thisapplication. The intended scope of the techniques of this applicationthus includes other structures, systems or methods that do not differfrom the techniques of this application as described herein, and furtherincludes other structures, systems or methods with insubstantialdifferences from the techniques of this application as described herein.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the scopeof the present disclosure. The present examples are to be considered asillustrative and not restrictive, and the intention is not to be limitedto the details given herein. For example, the various elements orcomponents may be combined or integrated in another system or certainfeatures may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

What is claimed is:
 1. A method for communication in a wirelesstelecommunication system, the method comprising: designating, by anetwork element, a first set of time-frequency resources fortransmitting a first set of downlink control channels for a plurality ofuser equipment (UEs), wherein the first set of time-frequency resourcesis known to the plurality of UEs, and wherein the first set oftime-frequency resources varies from a first time interval to a secondtime interval, wherein the first set of time-frequency resourcescomprise at least one of consecutive or distributed resources designatedfor an enhanced physical downlink control channel (E-PDCCH); mapping, bythe network element, a first region of the E-PDCCH to the first set oftime-frequency resources; and transmitting, by the network element, theE-PDCCH in a subframe comprising a physical downlink control channel(PDCCH) and a physical downlink shared channel (PDSCH), wherein theE-PDCCH is transmitted simultaneously with the PDSCH in afrequency-division multiplexing manner such that the E-PDCCH occupiesdifferent resource blocks (RBs) than the PDSCH, wherein resourceallocation configuration of the first set of time-frequency resources isdynamically signaled through an enhanced physical control formatindicator channel (E-PCFICH) that is transmitted earlier in time thanthe E-PDCCH.
 2. The method of claim 1, wherein the first set of downlinkcontrol channels carry downlink control information (DCI) common to aplurality of UEs.
 3. The method of claim 2, wherein a DCI in the firstregion of the E-PDCCH carries information associated with a systeminformation radio network temporary identifier (SI-RNTI).
 4. The methodof claim 3, wherein the DCI in the first region of the E-PDCCH carriesthe same scheduling information that is carried on a legacy controlregion in the PDCCH of the same subframe for a plurality of UEs, whereinthe DCI is transmitted with its cyclic redundancy check (CRC) bitsscrambled by the system information radio network temporary identifier(SI-RNTI).
 5. The method of claim 2, wherein a DCI in the first regionof the E-PDCCH carries information associated with a paging radionetwork temporary identifier (P-RNTI).
 6. The method of claim 1, whereinthe first region of the E-PDCCH carries information specific to a singleUE.
 7. The method of claim 6, wherein the first region of the E-PDCCHincludes downlink control information (DCI) associated with a cell radionetwork temporary identifier (C-RNTI).
 8. The method of claim 1, furthercomprising: mapping a second region of the E-PDCCH to the first set oftime-frequency resources, wherein DCls within the first and the secondregions are cross-interleaved and distributed over the first set oftime-frequency resources, the first and second regions defining a commonsearch space and a UE-specific search space, wherein the E-PDCCHoccupies a pair of non-adjacent RBs spanning two slots of the subframe,each RB in the pair allocating resource elements (REs) shared by thecommon search space and the UE-specific search space.
 9. The method ofclaim 1, further comprising: designating a second set of time-frequencyresources for at least a second region of the E-PDCCH, wherein thesecond region is a localized transmission region that is exclusively fora UE-specific search space, and wherein the first region of the E-PDCCHis a distributed region in which consecutive available time-frequencyresources are allocated for the UE-specific search space and a commonsearch space in the E-PDCCH.
 10. The method of claim 9, wherein separateRBs are allocated to the first and the second sets of time-frequencyresources such that resource elements (REs) in the first region of theE-PDCCH do not overlap with REs in the second region of the E-PDCCH. 11.A network element comprising: a processor configured such that thenetwork element: designates a first set of time-frequency resources fortransmitting a first set of downlink control channels for a plurality ofuser equipment (UEs), wherein the first set of time-frequency resourcesis known to the plurality of UEs, and wherein the first set oftime-frequency resources varies from a first time interval to a secondtime interval; maps a first region of an enhanced physical downlinkcontrol channel (E-PDCCH) to the first set of time-frequency resources;and transmits the E-PDCCH in a subframe comprising a physical downlinkcontrol channel (PDCCH) and a physical downlink shared channel (PDSCH),wherein the E-PDCCH is transmitted simultaneously with the PDSCH in afrequency-division multiplexing manner such that the E-PDCCH occupiesdifferent resource blocks (RBs) than the PDSCH, wherein the first set oftime-frequency resources comprise at least one of consecutive ordistributed resources designated for the E-PDCCH, wherein resourceallocation configuration of the first set of time-frequency resources isdynamically signaled through an enhanced physical control formatindicator channel (E-PCFICH) that is transmitted earlier in time thanthe E-PDCCH.
 12. The network element of claim 11, wherein the first setof time-frequency resources occupies a first pair of RBs and a secondset of time-frequency resources occupies a second pair of RBs, each RBin the first and second pairs comprising a known subset of the totalresources used to transmit the E-PDCCH in the subframe, and wherein thefirst pair of RBs comprise resource elements (REs) allocated only for acommon search space in the E-PDCCH and the second pair of RBs compriseREs allocated only for a UE-specific search space in the E-PDCCH. 13.The network element of claim 11, wherein the first set of time-frequencyresources is allocated to a distributed region in the E-PDCCH which isused to transmit downlink control information (DCI) common to at leastone UE.
 14. The network element of claim 11, wherein the network elementinforms the UEs to detect a common search space in the first region ofthe E-PDCCH.
 15. The network element of claim 11, wherein the first setof time-frequency resources define a common search space that is presentin every subframe in which an enhanced physical downlink control channel(E-PDCCH) is present.
 16. A method for communication in a wirelesstelecommunication system, the method comprising: mapping, by a networkelement, an enhanced physical downlink control channel (E-PDCCH) thatcarries downlink scheduling information to a user equipment (UE) toindicate a downlink data transmission over a physical downlink sharedchannel (PDSCH) to the UE, into a plurality of enhanced control channelelements (eCCEs), wherein each eCCE consists of a number of predefinedresource elements (REs) in a resource block (RB) pair, wherein the RBpair containing the plurality of eCCEs is signaled to the UEsemi-statically using radio resource control (RRC) signaling; andlinking, by the network element, a resource index of a physical uplinkcontrol channel (PUCCH) to an index of one of the plurality of eCCEs,wherein the PUCCH is provided for transmitting, by the UE, back to thenetwork element, a positive acknowledgement (ACK) or a negativeacknowledgement (NACK) about a decoding status of the PDSCH.
 17. Themethod of claim 16, wherein the eCCEs are a subset of a set of eCCEswhich are consecutively indexed and configured for possible E-PDCCHtransmission to the UE.
 18. The method of claim 17, wherein the eCCEsare arranged in multiple regions of the E-PDCCH, and wherein the E-PDCCHis multiplexed with the PDSCH.
 19. The method of claim 17, wherein anoffset value is associated with each set of eCCEs.
 20. The method ofclaim 19, wherein the offset values are signaled to the UEsemi-statically using higher layer signaling.
 21. The method of claim19, wherein the resource index of the PUCCH is obtained by adding theindex of one of the eCCEs to the offset value.
 22. A network elementcomprising: a processor configured such that the network element maps anenhanced physical downlink control channel (E-PDCCH) that carriesdownlink scheduling information to a user equipment (UE) to indicate adownlink data transmission over a physical downlink shared channel(PDSCH) to the UE, into a plurality of enhanced control channel elements(eCCEs), wherein each eCCE consists of a number of predefined resourceelements (REs) in a resource block (RB) pair, wherein the RB paircontaining the plurality of eCCEs is signaled to the UE semi-staticallyusing radio resource control (RRC) signaling; and the processor furtherconfigured such that the network element links a resource index of aphysical uplink control channel (PUCCH) to an index of one of theplurality of eCCEs, wherein the PUCCH is provided for transmitting, bythe UE, back to the network element, a positive acknowledgement (ACK) ora negative acknowledgement (NACK) about a decoding status of the PDSCH.23. The network element of claim 22, wherein one of the plurality ofeCCEs is the eCCE with the smallest index value.
 24. The network elementof claim 22, wherein one of the plurality of eCCEs is the eCCE with thelargest index value.